In the Classroom
An Example of a Guided-Inquiry, Collaborative Physical Chemistry Laboratory Course Alice A. Deckert* and Lisa P. Nestor Department of Chemistry, College of Holy Cross, Worcester, MA 01610 Donna DiLullo Department of Biology and Chemistry, Springfield College, Springrfield, MA 01109-3797
The last decade has seen fundamental changes in the way chemistry is taught. Many innovative and successful reforms focus on the first four semesters of college chemistry (1–13). However, relatively few innovations have been reported for the final four semesters of the chemistry major (14–19). These courses, which generally include physical, analytical, and inorganic chemistry, are also in need of reform (20). Because innovative curricula have been implemented in the first four semesters of chemical education, students come to expect a high level of instrumental and scientific sophistication. If no changes are made to bring at least the same level of sophistication to the final four semesters of the curriculum, students who elect to continue their study of chemistry may become disillusioned. We have recently attempted to apply accepted strategies of guided-inquiry and collaborative learning to a physical chemistry laboratory course. Our effort builds on the successful guided-inquiry approach used in many general and organic chemistry courses (1). The goals of this effort were threefold: 1. Guide students toward planning their own experiments, independent data analysis, and independent data interpretation. 2. Increase student preparedness for and intellectual engagement in the laboratory investigations. 3. Give students an understanding and appreciation of a collaborative work environment.
The structure of the laboratory course is discussed in the following section. In the remaining sections, student and faculty comments and suggestions are reported and several examples of successful investigations are given. Structure of the Lab Course A 12-week semester was divided into four 3-week blocks. Students were divided into lab groups of three to four students. These groups remained the same throughout the semester and functioned as a research team. During each of the time blocks teams were charged with answering a specific scientific question. Each group elected a principal investigator (PI) whose task was to lead the team effort. The role of PI was rotated during the semester allowing each member of the team to be in a leadership role for one investigation. The laboratory manual provided students with the question to be investigated and a list of the chemicals and instrumentation available to them. Background information was provided on theories or experimental techniques that might be needed to answer the question. Posted in the laboratory were specific instructions on how to operate each *Corresponding author. Current address: Department of Chemistry, Allegheny College, Meadville, PA 16335.
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instrument. Using this information, the lab groups were required to frame a proposal for how the question could be answered using available supplies and instrumentation. Each team was given two 4-hour laboratory periods to obtain the data necessary to answer their question. This restricted time frame placed an emphasis on pooling of data and gave students an understanding of the collaborative nature of any scientific investigation. The third 4-hour laboratory period in the 3-week block was used for group analysis and interpretation of data. Each lab group met with the instructors to orally present their research proposal sometime prior to the first week of the investigation. A written rough draft was handed in at this time. The instructors suggested any necessary changes and the final written draft of the proposal was due during the first week of the data-gathering phase. Requiring students to develop and discuss a well-thought-out experimental plan was designed to meet our first and second goals. Not only do students come to lab better prepared, they are more likely to be active participants during the lab. Students retain knowledge that is “constructed” (21, 22). By constructing a logical experimental procedure and presenting this in the form of a proposal, students obtain a deeper understanding of the process of science. During the first week of the investigation, the lab instructors were on hand to answer questions pertaining to instrumentation. In subsequent weeks, team members who had hands-on experience with each instrument instructed the other team members on the use of the apparatus. Any questions about technique were directed first to the appropriate team member. Only after exhausting the team’s resources could the instructors be called on to clarify use of an experimental apparatus. This required students to “peer teach”. This learning strategy has been documented as successful (23, 24 ). Students were asked to hand in their analyzed data after each week of the data-gathering phase. The instructor checked the data analyses to ensure that teams were using correct numbers as a basis for their interpretation of pooled data. This ensured that all team members participated in analyzing the data and that all data would be correctly analyzed by the third week of the block. In this way, teams could use the third week of the investigation to compile the data and discuss their interpretation rather than to analyze the raw data. During data analysis, peer teaching was again evident. Students who had performed a particular analysis successfully helped team members who had difficulties. In addition, each team was able to arrive at meaningful interpretations of their pooled data with minimal input from the instructors. The goal of independence from the instructor in data analysis and data interpretation was met to a significant degree.
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In the Classroom
The final requirement was the submission of a paper in the form of a journal article detailing the investigation. The high level of scientific writing exhibited in the final papers was a strong indication of the success of this reform effort. The experimental sections were well thought out and thorough, without plagiarizing the laboratory manual. In addition, the results and discussion sections were logical and well written. Each paper clearly benefited from the input and proof reading of multiple members of a team. Assessment of Student Work Each student received a course grade that represented the performance of the whole group as well as the performance of the individual. Each group received a common score for experimental design and final dissemination of results. Each student received an individual score for accuracy and precision of data, participation while in lab, and ability to analyze data correctly. The group score for experimental design was based on the oral presentation of the proposal and the final written draft. The group was also given a score for the final paper. Individual grades were based on the student’s laboratory notebook, observation of the student’s conduct in the laboratory, and the data analyses collected weekly. Student and Faculty Response A questionnaire administered to students after the first year of the program revealed two dissatisfactions, which were addressed by modifying the course structure in the second year. The first criticism expressed by the students was that teams could not find time outside of class to work on the projects for the course. The second was that the instructors were not aware of the performance of individuals and could not properly assess individual grades. Two modifications were made, which strengthened the course while increasing students’ satisfaction with their laboratory experience. During the first year of the program, students were allowed three laboratory periods to collect data and were expected to pool and discuss these data on their own time. Individual data analyses were submitted with the final paper rather than on a weekly basis. The first modification was to provide an entire laboratory period for teams to discuss and pool data. This meant that fewer tasks were performed outside of class, where the instructor would have no direct knowledge of the performance of individuals within the group. The second modification was to require the weekly submission of data analyses. This ensured that individual students kept up with the data analysis and provided the team with weekly feedback. The responses to the questionnaire indicate that, in general, students thought the specific objectives of this reform were met. Of the 31 students who responded, 55% agreed that the course had encouraged creativity and 49% thought that independence was encouraged; in both cases, 40% were neutral. Moreover, 65% of the students felt that they were more aware of skills and expectations needed to survive in a “real” research environment and 65% said that the experience had enhanced their conflict-management skills and enabled them to work more effectively with others. Students did not perceive a compromise in the instructors’ ability to provide guidance. Out of 31 responses, 81% indicated that the objectives and expectations were clear throughout the course. In addition, 81% of students felt that
they received adequate feedback on their performance. The faculty also feel that the specific goals of this reform have been met. They unanimously agree that students come to lab better prepared and more eager to work. This improved level of preparation among the students increases the level of discussion about the experiments during the laboratory period. In addition, the availability of expert peers within the teams frees the faculty from answering routine questions and fosters an atmosphere of collaboration and independence. From an instructor’s point of view, this peer teaching was perhaps the most exciting consequence of the reform. Not only were students cementing knowledge by teaching their peers, they were engaged and active participants in each 4-hour laboratory session. On the surface, this course structure appears to consume more faculty time than the traditional lab. However, in our experience this is not true. The preparation time for each experiment is no different than for a traditional laboratory. The biggest differences in time commitment are at the beginning of each 3-week block. At the beginning of each block, instructors must meet with each team to discuss specific experimental plans. This requires some extra time, but the increased independence of students during the laboratory periods that follow makes up for the initial effort. In addition, the work of grading lab reports is reduced to one paper per group per investigation. Not only is the quantity of reports decreased, the quality is increased to the point that grading the final papers is enjoyable. Sample Investigation
Calorimetry The question posed to the students was: “What is the ∆H hyd of sodium acetate and what is the best calorimetric method for the determination of ∆Hhyd?” Students had available two bomb calorimeters, a solution calorimeter with a solids sample cell, and a differential scanning calorimeter (DSC). Standards for calibrating each calorimeter were available, along with sodium acetate anhydrous and sodium acetate trihydrate. This lab requires students to use thermodynamic cycles, understand the concept of the standard state, and practice three common calorimetric techniques. In addition, they are required to think critically about experimental design and appropriate instrumentation. By comparing and contrasting the three methods for determining the heat of hydration of sodium acetate they see first-hand how cumulation of errors affects experimental outcomes. Table 1 presents the averages of all student data obtained for this investigation.
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In the Classroom
Physical Properties The question posed to the students for this investigation was: What types of intermolecular forces (excluding hydrogen bonding) are most important in determining the properties of a series of liquids? Students could measure vapor pressure as a function of temperature, dipole moments, density and viscosity. They were given a supply of acetone, 2-butanone, and 2-pentanone. Hexane, necessary for the measurement of dipole moments (25), was also available as a nonpolar solvent. This lab is designed to challenge students’ notion that ion–ion forces are the “strongest” intermolecular forces and that induced-dipole–induced-dipole forces are the “weakest”. Since each type of intermolecular force has a unique dependence on distance, induced-dipole–induced-dipole (dispersion) forces usually have a much greater collective effect on the physical properties of a liquid than the “stronger” dipole– dipole forces. In addition, this lab requires students to present correlations between two measurable variables. Table 2 presents the averages of all student data obtained for this investigation. Isomerization of Push-Pull Azobenzenes The question posed in this investigation is: What is the more likely mechanism for the isomerization of push-pull azobenzenes: inversion or rotation? Students have a flash photolysis unit available with a variable temperature cell and circulating water bath. Also available are a range of solvents and three azobenzene derivatives. The derivatives are chosen to provide a variety of donor groups. This investigation is designed so that students think critically about the process of proposing a mechanism for a reaction. Push-pull azobenzenes undergo a cis-trans isomerization, which can be studied using flash photolysis. The cis isomer is prepared photochemically and the relaxation back to the trans isomer is observed. The mechanism for this isomerization has been argued in the literature (26–29). Both an inversion mechaism and a rotation mechanism have been proposed. Students were told that they must support one of these mechanisms based on their data. The change in rate constant when the solvent and donor substituent are changed point to a dipolar transition state such as is necessary for a rotation mechanism (26–29). However, the temperature dependence results in a slightly negative entropy of activation, which is consistent with an inversion mechanism (26, 27). These contradictory pieces of information present students with a dilemma they must resolve in order to present the project in final form. Tables 3 and 4 present the averages of all student data for this investigation.
the instructor throughout the investigation (1–13). This reform of the physical chemistry laboratory course was undertaken to build on the successful programs implemented in the first four semesters of the chemistry curriculum at many institutions. In addition, there was a real frustration with ill-prepared students and student apathy in the physical chemistry lab. Our reform has answered these challenges in many ways. Students cannot come to lab ill prepared. Without a plan they are not allowed to perform any experiments. Because students must construct their own experimental protocol, they are actively engaged with the investigation from the very beginning. Students are more likely to actively participate in the investigation if questions are designed to pique their interest. In the examples given, students are asked to answer two types of questions. Some questions are designed so that students are not likely to know the answer (calorimetry and cis-trans isomerization kinetics). Other questions confront common misconceptions (physical properties). Students may think they know the answer before beginning, but are soon forced to face a misconception and reconcile their data with their flawed intuition. Finally, students often have unrealistic expectations about
Conclusions The initiative described here employs many of the learning techniques that have been found to be successful for first- and second-year college science teaching. Students are required to construct their knowledge of an investigation by forming an experimental plan (21, 22). They are required to collaborate on relatively open-ended 3-week projects (1–13, 23, 24). They are actively engaged by peer-teaching learning strategies (23, 24) and they are guided by
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how science is done. The long-held belief that science is a solitary pursuit done by people in white lab coats who seldom stop to eat or sleep—let alone talk to another human being— is unfortunately alive and well. Our approach to a physical chemistry laboratory course confronts this misconception head on. More than half of the activities are performed as a group. Students quickly realize that developing skills to work within a group and collaborate on a project is at least as important as obtaining good results and understanding the chemistry involved in the project. This should prove to be the single most valuable lesson that students learn from this approach to physical chemistry laboratory. Acknowledgment This work has been supported by the National Science Foundation through grant number DUE-9455928, Establishing New Traditions: Revitalizing the Curriculum, awarded to the University of Wisconsin, Madison, WI.
7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.
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